A large portion of carpets used in residences are known as pile carpets formed by tufting pile yarn into a primary backing material. The yarns tufted into the primary backing form the fibrous face of the carpet. The tufted loops can optionally be cut or sheared to form tufts of a desired, constant vertical height.
Two general categories of tufted carpets are (1) a textured style, in which the tufts and the individual filaments or staples have varying degrees of crimp or curl; and (2) a straight-set style, in which the filaments or staples at the tuft tip are straight and substantially perpendicular to the plane of the carpet face. Addressing the first category of carpets, yarn that is used as pile in textured style carpets is prepared by cabling together a plurality of single yarns and setting them in their twisted condition. One option is to use a stuffer box to produce textured yarn having a desirable appearance and texture when tufted into the primary backing. The purpose of the stuffer box is to put texture in the twisted yarn. Stuffer boxes are well know in the art and are exemplified by one major stuffer box brand that uses the tradename Superba®.
During operation of such a stuffer box, uncrimped yarn is transported by a pair of counter-rotating nip rolls into and through a confined zone within the interior of the stuffer box. There, the yarn is caused to be folded and compressed into a fine crimp configuration. The crimps in the yarn can then be heat set, which “locks in” or sets the texture to make it of a lasting nature. The more the yarns are textured, the lighter the color because more light is reflected from the crimps and elbows formed into the yarns.
The latter type of carpet, the straight-set style, does not use a stuffer box in the production line. As such, the filaments or staples at the tuft tip are straight and substantially perpendicular to the plane of the carpet face. Without processing the yarns through a stuffer box and texturizing the yarns prior to tufting into the primary backing, the untextured carpet has a darker appearance than that of a carpet that was formed using the identical yarn strands processed in a stuffer box and then heat set.
The textured-style carpets are more popular than the straight-style carpet because, for example, the texturizing characteristics assist in hiding footprints and vacuum tracks. The step of texturizing the yarns with the stuffer box, however, creates some issues that do not exist when producing the straight-style carpet. One such recurring problem arises after a shutdown of the heat-set production line, which occurs periodically for doffing the winders, other planned line stops, and aberrant conditions that may arise during operations. Once operations resume, some of the yarns have a lighter appearance than yarns processed during normal operating conditions, i.e., before and after the shutdown.
It has been found that the yarns remaining within the stuffer box during and through the shutdown result in lighter colors due to overcrimping. The yarn remains in the stuffer box and cools, allowing the finish on the yarn to coagulate. This yarn obtains too much texture by remaining in the stuffer box longer than the normal processing time. The lighter appearance of the overly textured yarns is particularly apparent when they are tufted into the primary backing and appear as light streaks in fiberous face of the tufted carpets. These lighter sections of the tufted carpet, located between yarns processed by the stuffer box during normal operations, are unacceptable from a quality-control standpoint and are not marketable.
Additionally, the current stuffer box configuration contains a number of pinch-points wherein portions of the yarn filaments get caught, causing the heat-set production line to be shut down by the operator.